Earlier today, former Florida Gov. Jeb Bush (R) came out against a pathway to citizenship for undocumented immigrants, reversing his previous position on the central tenet of comprehensive immigration reform.

According to a copy of Bush's new book "Immigration Wars," obtained by ABC News, the ex-governor's plan specifically rules out the possibility of undocumented immigrants obtaining full citizenship if they remain in the United States. Bush makes an exception for young undocumented immigrants, known as DREAMers, who were brought to the U.S. as minors.

"Permanent residency in this context, however, should not lead to citizenship. It is absolutely vital to the integrity of our immigration system that actions have consequences -- in this case, that those who have violated the laws can remain but cannot obtain the cherished fruits of citizenship," Bush writes in the book, which was co-authored with conservative attorney Clint Bolick. "To do otherwise would signal once again that people who circumvent the system can still obtain the full benefits of American citizenship. It must be a basic prerequisite for citizenship to respect the rule of law."

Bush goes on to call full citizenship for undocumented immigrants an "undeserving reward for conduct we cannot afford to encourage."

Immigrants who came to the United States without documentation as adults could apply for permanent legal residency as follows:

1. Plead guilty to having committed the crime of illegal entry.

2. Pay fines, perform community service, or adhere to another form of punishment prescribed by the law. (Those who do not come forward during this process are subject to automatic deportation if they remain in the U.S.)

3. Immigrants who follow step two must then pay back taxes, learn English, and refrain from committing "substantial crimes" in order to earn permanent legal residency.

The only means through which undocumented immigrants can earn U.S. citizenship under the Bush plan would be to return to their home countries and apply through existing legal means. But these undocumented immigrants would be subject to either a three- or ten-year bar if they return and apply for U.S. citizenship from their home country.

An immigrant who enters the United States without inspection (illegally), or who overstays a period of admission by more than 180 days, but less than one year, and who then departs the U. S. voluntarily, is barred from being re-admitted or re-entering the United States for three years. If an immigrant is in the country illegally for more than one year, a ten year bar to admission applies.

"We need to address this problem in a fair, firm, and comprehensive way, while at the same time fixing our immigration process so that in the future, millions of people do not feel the need to enter our country illegally because there are no viable means for them to do so lawfully," write Bush and Bolick.

Bush makes an exception for DREAMers. Bush's plan would provide a "clear and definite path to citizenship" for young immigrants who earn a high school diploma or GED, or serve in the military, were brought to the U.S. before the age of 18, resided in the U.S. for at least 5 years, and have a criminal record clear of any "significant crimes."

These children would not have to plead guilty to a crime or suffer legal consequences. They could obtain the existing form of permanent legal residency (otherwise known as a green card). From there, they could apply for citizenship after five years.